Break away support for 3d printing

ABSTRACT

In one example, a 3D printing system includes a support structure generator to identify a breakaway support to temporarily support part of the object, to design a wedge shaped groove between a portion of the object and the support, the groove ending at a line along which the support intersects the object, and to generate a digital object model that includes the support and the groove. The system also includes a 3D printer to print the object, support and groove based on the object model.

BACKGROUND

3D printers convert a digital representation of an object into thephysical object. 3D printers are used to manufacture objects withcomplex geometries using a variety of materials includingthermoplastics, polymers, ceramics and metals. In powder based 3Dprinting, successive layers of a powdered build material are formed andportions of each layer solidified in a desired pattern to build up thelayers of the 3D object.

DRAWINGS

FIG. 1 illustrates an example support structure generator to generate adigital representation of breakaway supports and corresponding groovesor other breakaway force concentrating features.

FIG. 2 illustrates an example implementation for a support structuregenerator shown in FIG. 1 .

FIG. 3 illustrates an example additive manufacturing system with a 3Dprinter to print green parts and a sintering furnace to sinter the greenparts.

FIGS. 4-6 illustrate an example object structure with a breakawaysupport.

FIGS. 7 and 8 are details from FIGS. 5 and 6 , respectively.

FIG. 9 illustrates an example modified object model with object slicesto print a structure shown in FIGS. 4-6 .

FIG. 10 presents a series of sections corresponding to the slice imagesin the example object model shown in FIG. 9 .

FIG. 11 illustrates an example method for modifying an object model togenerate slices to print breakaway force concentrating grooves.

FIGS. 12-17 illustrate other example object structures with a breakawaysupport.

The same part numbers designate the same or similar parts throughout thefigures. The figures are not necessarily to scale.

DESCRIPTION

Metal objects may be produced, for example, by selectively applying aliquid binder agent to portions of each of successive layers of metalpowder to bind together those portions of the powder corresponding tothe solid layer of the 3D object. The binder agent is dried or otherwisecured, for example using heat and/or ultra violet energy. The curedobject, known commonly as a “green part”, is heated in a sinteringfurnace to burn off any residual binder and fuse the metal. Structuresmay be formed with the green part for support during sintering toprevent the part from tipping and/or to inhibit sagging of overhangs andother spans that are otherwise inadequately supported within the objectitself. The support structures are separated from the object afterfusing, usually by breaking the supports away from the object.

A new support structure has been developed to concentrate the breakawayforce for easier separation. In one example, the support structureincludes a wedge shaped groove between the object and the support. Thegroove narrows to a line along which an inner portion of the supportintersects the object. The groove concentrates the breakaway force alongthe line of intersection to reduce the force needed to initiateseparation. Also, the line of intersection at the base of the grooveforms a nascent crack to more consistently initiate separation at thedesired location and for cleaner separation, particularly for a unifiedstructure in which each support is printed from the same material as theobject with no intervening separation layer. Although a straight groovemay be used, a wedge shaped groove facilitates removing powder from thegroove before sintering.

An object model for printing a force concentrating, breakaway supportstructure may be generated, for example, by modifying the object modelto include supports and grooves (or other force concentrating features)based on the geometry of the object, characteristics of the buildmaterial, the precision of the printer, the desired breakaway force andany other relevant parameters. Object model analysis and modeling forbreakaway supports may be implemented through programming on the printercontroller, by an object model processor distinct from the printercontroller, or as part of the original object model using 3D modelingsoftware adapted to create the new support structures.

Examples of the new structures are not limited to metal or ceramic“green parts” sintered/fused after printing, but may be used withpolymers and other materials fused during printing. Also, althoughexamples are described with reference to force concentrating grooves,other breakaway force concentrating features are possible. Accordingly,the examples described herein illustrate but do not limit the scope ofthe patent which is defined in the Claims following this Description.

As used in this document, “and/or” means one or more of the connectedthings; a “memory” means any non-transitory tangible medium that canembody, contain, store, or maintain information and instructions for useby a processor and may include, for example, circuits, integratedcircuits, ASICs (application specific integrated circuits), hard drives,random access memory (RAM), read-only memory (ROM), and flash memory;and a “span” means any part of an object supported by, or to besupported by, a breakaway support during printing or post printprocessing.

FIG. 1 illustrates one example of a support structure generator 10 togenerate a digital representation of breakaway supports andcorresponding grooves or other breakaway force concentrating features.Generator 10 may be implemented, for example, through programming on aprinter controller, an object model processor separate from the printercontroller, or as part of a 3D modeling program. Generator 10 includesan object model analyzer 12 to analyze an object model 14. Object modelanalyzer 12 may, for example, analyze object model 14 to determine theintended orientation of the object during printing, post printsintering, and/or other post print processing, and then determinebreakaway supports for parts of the object in one or multiple intendedorientations.

Support structure generator 10 also includes a support structuredesigner 16 to design support structures to be added to object model 14based on analyses by object model analyzer 12. Designer 16 includes agroove generator 18 to generate a force concentrating groove or multiplegrooves for each breakaway support in which it is determined that such agroove or grooves is desired. Generator 10 generates a modified objectmodel 20 that may be used to print the object and support structures. A3D printer may be controlled based on digital slices taken from themodified object model to apply a binder or fusing agent to each ofsuccessive layers of build material in a pattern corresponding to eachlayer/slice of the object.

FIG. 2 illustrates one example implementation for a support structuregenerator 10 shown in FIG. 1 . Referring to FIG. 2 , generator 10includes a processor 22, such as a microprocessor or microcontroller, amemory 24, and a communications bus 24 connecting processor 22 andmemory 24. Memory 24 stores object model analyzer instructions 28 that,when executed by processor 22, cause the processor to analyze an objectmodel. Memory 24 also stores support structure designer instructions 30with groove generator instructions 32 that, when executed by processor22, cause the processor to modify an object model to include breakawaysupport structures and corresponding force concentrating grooves. In oneexample, memory 24 with instructions 28, 30, and 32 is part of a printercontroller along with processor 22 and bus 26. In another example,memory 24 with instructions 28, 30, and 32 is part of a 3D modelingprogram.

FIG. 3 illustrates one example of an additive manufacturing system 34with a 3D printer 36 to print green parts and a sintering furnace 38 tosinter the green parts. Referring to FIG. 3 , in this example printer 36is implemented as a binder jet type 3D printer for printing green parts42 through the application of a liquid binder to each of successivelayers of powdered build material. Printer 36 includes a build chamber40 in which the green parts are printed. In the example shown in FIG. 3, each green part is printed as unified structure 42 that includes anobject 44 and a support 46 integral to and made of the same material asobject 44. Structure 42 is described in more detail below with referenceto FIGS. 4-6 .

Structures 42 are printed on a build platform 48 that moves verticallyin chamber 40 to accommodate the formation of each successive layer ofpowdered build material 50 by a layering system 52. Once a layer ofbuild material has been printed, the build platform is lowered adistance corresponding to the thickness of the next layer of buildmaterial to be formed atop the previous layer. Any suitable buildmaterial powder 50 may be used including, for example, metals, ceramics,and polymers. A layering system 52 may include, for example, a roller,wiper, blade or any other mechanism suitable for forming layers of buildmaterial over platform 48.

Printer 36 in FIG. 3 includes an agent applicator 54 to selectivelyapply a liquid binder to individual layers of build material in adesired pattern based on the modified object model 20 (FIG. 1 ). Agentapplicator 54 may be implemented, for example, as an inkjet printhead oran array of multiple inkjet printheads. In this example, printer 36 alsoincludes an energy source 56 to dry and/or cure the binder to form greenparts 42. The green parts are transferred from build chamber 40 tosintering furnace 38 to fuse the green material for the completedobject. Supports 46 are broken away from objects 44 after sintering.

A controller 58 in FIG. 3 includes the programming, processing andassociated memory resources, and the other electronic circuitry andcomponents to control the operative elements of printer 36. Inparticular, controller 58 may include programming to modify the objectmodel to print force concentrating grooves for the breakaway supports.Groove programming may be implemented in controller 58, for example,through a memory 24 with groove generator instructions 32 and aprocessor 22 to execute instructions 32, as described above withreference to FIG. 2 . Controller 58 may also include object modelanalyzer instructions 28 and support structure designer instructions 30shown in FIG. 2 .

FIGS. 4 and 5 illustrate one example of an object structure 42 with anobject 44 and a breakaway support 46. Structure 42 may be a green partor a fully fused part before breaking away the support. Object 44includes a span 60 supported by support 46. In this example, span 60 isan overhang. Structure 42 includes a groove 62 between object 44 andsupport 46. In this example, groove 62 is a wedge shaped groove thatends at a line 64 along which an inner portion of support 46 intersectsspan 60. Also in this example, groove 62 is defined by a bevel 66 alonga top part of support 46 and a flat 68 (not beveled) along a bottom partof span 60. FIG. 6 shows support 46 breaking away from object 44 at theurging of a breakaway force 70 applied to the bottom part of support 46.

Referring to the detail of FIG. 7 , the breadth 73 of the physical line64 along which along which an inner portion of support 46 intersectsspan 60 is the printed equivalent of at least one voxel. Unlike amathematical line, a physical line necessarily has breadth. The breadthof a printed voxel depends on the precision of the 3D printer. Thinnerlayers of build material and higher resolution agent applicators may beused to produce a narrower voxel and thus a sharper line 64. Similarly,the angle 72 of bevel 66 with respect to flat 68 is approximated by aseries of tiny steps 74 along support 46. Unlike milling machines andother subtractive analog manufacturing tools, 3D printers may not beable produce a continuous, smooth bevel. 3D printing is additive anddigital. Consequently, a bevel is approximated by applying a binder orfusing agent digitally, voxel by voxel, turning the applicator on andoff to apply the desired pattern of agent to each of successive layersof build material, producing steps 74 shown in FIG. 7 . Thinner layersof build material and higher resolution agent applicators may be used toproduce a better approximation of a smooth, continuous bevel.

Groove 62 concentrates the breakaway force 70 along line 64 to reducethe force to initiate a break between support 46 and from object 44. Agroove 62 may be designed to initiate the break at a force 70 (FIG. 6 )below a threshold force when force 72 is exerted on support 46. Inaddition, groove 62 may be designed to facilitate removing powder fromthe groove. Although a straight groove may be used to achieve thedesired breakaway force, a wedge shaped groove facilitates removingpowder from the groove while still allowing a narrow line ofintersection 64. This is particularly desirable for green parts, whichare depowdered before sintering. Any significant amount of powder in agroove 62 may become fixed and attached to the surrounding parts,causing a larger breakaway force and less clean fracture line.

The detail of FIG. 8 shows one example of fracture lines 76, 78 assupport 46 breaks away from object 44. The smoothness of fracture lines76, 78 may depend on the characteristics of the material forming support46 and object 44 as well as the breadth of line 64 and any unwantedpowder remaining in groove 62.

FIG. 9 illustrates a modified object model 20 with object slices 80 toprint a structure 42 shown in FIGS. 4 and 5 . Slices 80 may be part ofthe modified object model, as shown in FIG. 9 , or object slices 80 maybe generated separately from the modified object model, for example by a3D printer controller or by an object model processor distinct from theprinter controller. Object slices 80 represent multiple digital slicesused to print corresponding layers of the structure, as indicated byslice images 82A-82E in FIG. 9 . Slice images 82A-82E in FIG. 9correspond to layers 82A-82E in structure 42 shown in FIG. 10 .

FIG. 11 illustrates one example of a method 100 for modifying an objectmodel to generate slices 80 shown in FIG. 9 , to print a forceconcentrating groove 62. Method 100 may be implemented, for example, bya support structure generator 10 shown in FIG. 1 . Part numbers in thedescription of method 100 refer to FIGS. 4-10 . Referring to FIG. 11 ,the object model is analyzed to identify any spans 60 in object 44(block 102). Support(s) 46 and groove(s) 62 are designed for each spanto achieve the desired breakaway forces (block 104). The object model ismodified to include the support(s) and groove(s) (block 106). Objectslices are generated within the modified object model, or separatelybased on the modified object model, with each slice defining thoseportions of a layer of build material to be printed to form a structure42 that includes an object 44, support(s) 46, and groove(s) 62 (block108).

The design of each support and corresponding groove (or grooves) mayinclude the size, shape and location of the support as well as thefeatures that will be printed to define each groove. For example, themodified object model may define the length and angle of a bevel 66along support 46 and a flat 68 along object 44. The modified objectmodel may also set the resolution for printing steps 74, and thus thebreadth of line 64 and smoothness of angle 72, based on thecharacteristics of the build material, the thickness of each layer ofbuild material, the precision of the agent applicator, and the desiredbreakaway force. Printers with higher resolution and thus more preciseapplicators and that are able to form thinner layers may print narrowerlines 64 and smoother bevels 66.

FIGS. 12 and 13 illustrate another example of an object structure 42.Referring to FIGS. 12 and 13 , a straight groove 62 ends at the line ofintersection 64 between support 46 and span 60. The breadth 73 of groove62 may be as narrow as one voxel for a lower breakaway force and acleaner break. A broader groove 62, however, may desirable in someimplementations to facilitate removing powder from the groove.

In the example shown in FIG. 14 , structure 42 includes multiplesupports 46 supporting a tapered span 60 along a slope of the taper.Structure 42 includes grooves 62 at each side of each support 46.

In the example shown in FIG. 15 , an interface 86 is interposed betweenobject 44 and support 46. Groove 62 ends at a line 64 along which theinner portion of support 46 intersects interface 86. Interface 86further reduces the breakaway force and helps make a cleaner break.Examples of an interface 86 are disclosed in international applicationno. PCT/US2018/029968 filed Apr. 27, 2018 and titled SUPPORT STRUCTURESAND INTERFACES. In one example, an interface 86 is printed by applyingan interface agent that forms a localized weaker region of buildmaterial between object 44 and support 46. Depending on the type ofinterface agent, the physical properties of interface 86 may differ fromthose of object 44 and support 46. For example, some interface agentsmay include ceramic nanoparticles that weaken the interface betweenobject 44 and support 46 during binding or fusing. For another example,some interface agents may include chemicals that create gas pocketsbetween object 44 and support 46 during binding or fusing to weaken theinterface.

Referring now to FIGS. 16 and 17 illustrating another example of anobject structure 42. In this example, span 60 extends between parts 84of object 44 and structure 42 includes a groove 62 at each side ofsupport 46. A breakaway force may be applied to either side of support46 to initiate a break at the corresponding line 64. The opposite groove62 may also help support 46 separate more cleanly from object 44.

As noted at the beginning of this Description, the examples shown in thefigures and described above illustrate but do not limit the scope of thepatent. Other examples are possible. Therefore, the foregoingdescription should not be construed to limit the scope of the patent,which is defined in the following Claims.

“A” and “an” as used in the Claims means one or more.

1. A system comprising: a processor; and a memory storing instructionsexecutable by the processor to: identify a breakaway support to supportpart of an object; to design a groove between a portion of the objectand the support, the groove ending at a line along which the supportintersects and is integral or directly connected to the object; generatea digital object model that includes the support and the groove; andcause a 3D printer to print the object, support and groove based on theobject model.
 2. The system of claim 1, wherein the groove is awedge-shaped groove.
 3. The system of claim 1, further comprising the 3Dprinter.
 4. The system of claim 1, wherein the instructions areexecutable by the processor to further: generate multiple slices fromthe object model with each slice defining those portions of a layer ofbuild material to be printed to form the object, support and groove. 5.A non-transitory computer-readable medium storing instructions that,when executed by a processor, cause a 3D printing system to: analyze adigital model of an object; identify a breakaway support to support partof the object; design a structural feature, including a shaped groove,to concentrate a breakaway force along a line where the supportintersects and is integral or directly connected to the object; modifythe digital object model to include the support and the structuralfeature; and print the object, support and groove based on the modifieddigital object model.
 6. The non-transitory computer-readable medium ofclaim 5, wherein the groove is a wedge-shaped groove.
 7. Thenon-transitory computer-readable medium of claim 5, wherein theinstructions, when executed by the processor, further cause the 3Dprinting system to generate multiple slices based on or within themodified digital object model, with each slice defining those portionsof a layer of build material to be printed to form the support and thestructural feature.
 8. The non-transitory computer-readable medium ofclaim 5, wherein the instructions, when executed by the processor,further case the 3D printing system to: design the breakaway supportintegral to the object; and design, as the structural feature, theshaped groove between a portion of the object and the support, thegroove ending at the line along which the support intersects and isintegral or directly connected to the object.
 9. The non-transitorycomputer-readable medium of claim 5, wherein the non-transitorycomputer-readable medium is part of the 3D printing system, the 3Dprinting system including the processor.
 10. A method for 3D printing anobject, comprising: identifying, by a processor, a span; designing, bythe processor, a breakaway support to support the span; designing, bythe processor, a groove to concentrate a breakaway force along a linewhere the support intersects the span and is integral or directlyconnected to the span; generating, by the processor, digital objectslices to print the span, support, and groove; and printing, by theprocessor, the object using the digital object slices.
 11. The method ofclaim 10, wherein the groove is a wedge-shaped groove.
 12. The method ofclaim 10, further comprising: analyzing, by the processor, a digitalmodel of the object to identify the span; modifying, by the processor,the object model to include the support and the groove; and generating,by the processor, the digital object slices using a modified objectmodel.
 13. A physical object comprising: a span; a breakaway support totemporarily support the span; and a structural feature, including agroove, to concentrate a breakaway force along a line where the supportintersects the span and is integral or directly or directly connected tothe span.
 14. The physical object of claim 13, wherein the groove is awedge-shaped groove.
 15. The physical object of claim 13, wherein thegroove is between a portion of the span and the support, the groovenarrowing to the line along which an inner portion of the supportintersects the span.
 16. The physical object of claim 13, wherein thegroove is configured to initiate a break along the line in response to aforce, below a threshold force, exerted on the breakaway support.